In this study, I evaluate adherence to Nigeria's Language of Instruction (LOI) policy, which mandates that primary school students be taught in indigenous language. Using multivariate regression analysis and data from round 6 of the Multiple Indicator Cluster Survey (MICS6), I assessed disparities in adherence between school types (public and private schools) and location (urban/rural areas) and regions. The results reveal private schools exhibit lower implementation rates than public schools, while urban areas lag behind rural areas, and the southern region trails the north. This highlights the challenges of enforcing a uniform LOI policy in Nigeria's linguistically diverse setting. I also examine the relationship between LOI and literacy outcomes using regression and propensity score matching anaysis. Contrary to prevailing notion that teaching children in an indigenous language improves learning outcomes, my findings show that students taught in English outperformed their peers taught in indigenous languages. This departure from the norm underscores the need to reassess generalized conclusions derived from less lingustically diverse contexts, as they might not apply settings like Nigeria. It also calls for a nuanced understanding of how LOI influences learning outcomes in diverse contexts, emphasizing the importance of tailoring educational policies to local realities.